These reports explain that Plate Heat Exchangers (PHE) and Shell and Tube Heat Exchangers (S&T) have been used for many Navy and commercial marine shipboard cooling duties. However, certain features of the PHE can make it a more viable alternative than S&T coolers.

Alfa-Laval offers a full line of PHEs which have been in service worldwide with most shipping concerns for over 25 years. Since their introduction, more than 7,500 units have been put into marine service.

The company's PHE consists of a plate pack and a frame. The frame consists of a fixed plate to which all pipes are connected. An upper and lower carrying bar are supported by an outrigger or support column. The plate pack is suspended from the upper carrying bar and is clamped together by compression bolts.

The plate packs are pressed from titanium for seawater service and stainless steel for freshwater service.

The unit is normally installed by deck mounting but can be mounted in other configurations as well.

PHEs that are supplied to the U.S. Navy have met extensive requirements for shock and vibration.

According to Alfa-Laval, the alternating titanium plate and gasket design used in the configuration of PHEs prevents interleakage of the two fluids and allows the use of considerably higher liquid velocities without erosion. The corrugated Chevron design of the plates also gives the unit a considerably higher heat transfer coefficient and, therefore, requires less cooling water flows.

The company reports that PHEs have proven to be easily maintainable both in port and at sea. No special tools are required to disassemble, inspect and clean the unit.

The PHE offers excellent performance in close temperature approaches or hard-to-perform thermal duties such as cooling a liquid down to 100 degrees F when using 95 degree seawater. On many of the test and evaluations ships, the reports indicated that for the first time in years, the cooling system was able to meet the performance requirements and be available for service 100 percent of the time.

Light in weight and innovative in performance, the PHE lends itself to retrofitting, as the unit can be disassembled dockside into its component parts, hand-carried to the location of installation and reinstalled by the ship's force, eliminating the need for cranes, or removal of other equipment so that the exchanger can be put into place.

One of the most impressive features of the PHE is its ability to be modified in the field to compensate for changes in the thermal duty. A PHE can be expanded merely by adding plates, changing the plates, or, in the other extreme, by taking plates out.

For U.S. Navy combatant vessels, the Alfa-Laval plate heat exchanger has met and passed the requirements of both MIL-STD-167-1 vibration and MIL-STD-901C shock for Grade A, Class 1, hull-mounted machinery.

Applications from 0-1,000 gpm include seawater to fresh water, seawater to oil, and fresh water to fresh water.

Alfa-Laval is offering free color brochures on their line of marine plate heat exchangers. Through the use of color photographs, drawings, tables and explanatory text, the brochures fully detail the features and advantages of Alfa-Laval PHEs. For your free copies, Circle 36 on Reader Service Card